diff --git a/core/modules/file/src/Tests/FileFieldValidateTest.php b/core/modules/file/src/Tests/FileFieldValidateTest.php
index 9d43060..de3b1c5 100644
--- a/core/modules/file/src/Tests/FileFieldValidateTest.php
+++ b/core/modules/file/src/Tests/FileFieldValidateTest.php
@@ -71,8 +71,10 @@ function testFileMaxSize() {
     $field_name = strtolower($this->randomMachineName());
     $this->createFileField($field_name, 'node', $type_name, array(), array('required' => '1'));
 
-    $small_file = $this->getTestFile('text', 131072); // 128KB.
-    $large_file = $this->getTestFile('text', 1310720); // 1.2MB
+    // 128KB.
+    $small_file = $this->getTestFile('text', 131072);
+    // 1.2MB.
+    $large_file = $this->getTestFile('text', 1310720);
 
     // Test uploading both a large and small file with different increments.
     $sizes = array(
@@ -185,4 +187,25 @@ public function testFileRemoval() {
     $this->assertText('Article ' . $node->getTitle() . ' has been updated.');
   }
 
+  /**
+   * Test the validation message is displayed only once for ajax uploads.
+   */
+  public function testAJAXValidationMessage() {
+    $field_name = strtolower($this->randomMachineName());
+    $this->createFileField($field_name, 'node', 'article');
+
+    $this->drupalGet('node/add/article');
+    /** @var \Drupal\file\FileInterface $image_file */
+    $image_file = $this->getTestFile('image');
+    $edit = array(
+      'files[' . $field_name . '_0]' => $this->container->get('file_system')->realpath($image_file->getFileUri()),
+      'title[0][value]' => $this->randomMachineName(),
+    );
+    $this->drupalPostAjaxForm(NULL, $edit, $field_name . '_0_upload_button');
+    $elements = $this->xpath('//div[contains(@class, :class)]', array(
+      ':class' => 'messages--error',
+    ));
+    $this->assertEqual(count($elements), 1, 'Ajax validation messages are displayed once.');
+  }
+
 }
diff --git a/core/modules/image/src/Tests/ImageFieldValidateTest.php b/core/modules/image/src/Tests/ImageFieldValidateTest.php
index 5f0bf21..bf6b4df 100644
--- a/core/modules/image/src/Tests/ImageFieldValidateTest.php
+++ b/core/modules/image/src/Tests/ImageFieldValidateTest.php
@@ -8,6 +8,7 @@
  * @group image
  */
 class ImageFieldValidateTest extends ImageFieldTestBase {
+
   /**
    * Test min/max resolution settings.
    */
@@ -156,4 +157,26 @@ protected function getFieldSettings($min_resolution, $max_resolution) {
     ];
   }
 
+  /**
+   * Test the validation message is displayed only once for ajax uploads.
+   */
+  public function testAJAXValidationMessage() {
+    $field_name = strtolower($this->randomMachineName());
+    $this->createImageField($field_name, 'article');
+
+    $this->drupalGet('node/add/article');
+    /** @var \Drupal\file\FileInterface[] $text_files */
+    $text_files = $this->drupalGetTestFiles('text');
+    $text_file = reset($text_files);
+    $edit = array(
+      'files[' . $field_name . '_0]' => $this->container->get('file_system')->realpath($text_file->uri),
+      'title[0][value]' => $this->randomMachineName(),
+    );
+    $this->drupalPostAjaxForm(NULL, $edit, $field_name . '_0_upload_button');
+    $elements = $this->xpath('//div[contains(@class, :class)]', array(
+      ':class' => 'messages--error',
+    ));
+    $this->assertEqual(count($elements), 1, 'Ajax validation messages are displayed once.');
+  }
+
 }
diff --git a/core/tests/Drupal/KernelTests/Core/Render/RenderTest.php b/core/tests/Drupal/KernelTests/Core/Render/RenderTest.php
index 8860c19..6bb3bed 100644
--- a/core/tests/Drupal/KernelTests/Core/Render/RenderTest.php
+++ b/core/tests/Drupal/KernelTests/Core/Render/RenderTest.php
@@ -16,7 +16,7 @@ class RenderTest extends KernelTestBase {
    *
    * @var array
    */
-  public static $modules = array('system', 'common_test');
+  public static $modules = array('system', 'common_test', 'theme_test');
 
   /**
    * Tests theme preprocess functions being able to attach assets.
@@ -44,6 +44,23 @@ function testDrupalRenderThemePreprocessAttached() {
   }
 
   /**
+   * Ensures that render array children are processed correctly.
+   */
+  public function testRenderChildren() {
+    // Ensure that #prefix and #suffix is only being printed once since that is
+    // the behaviour the caller code expects.
+    $build = [
+      '#type' => 'container',
+      '#theme' => 'theme_test_render_element_children',
+      '#prefix' => 'kangaroo',
+      '#suffix' => 'kitten',
+    ];
+    $this->render($build);
+    $this->removeWhiteSpace();
+    $this->assertNoRaw('<div>kangarookitten</div>');
+  }
+
+  /**
    * Tests that we get an exception when we try to attach an illegal type.
    */
   public function testProcessAttached() {
diff --git a/core/tests/Drupal/Tests/Core/Render/RendererTest.php b/core/tests/Drupal/Tests/Core/Render/RendererTest.php
index 51cfde8..7e24134 100644
--- a/core/tests/Drupal/Tests/Core/Render/RendererTest.php
+++ b/core/tests/Drupal/Tests/Core/Render/RendererTest.php
@@ -363,6 +363,25 @@ public function providerTestRenderBasic() {
     };
     $data[] = [$build, 'baz', $setup_code];
 
+    // #theme is implemented but #render_children is TRUE. In this case the
+    // calling code is expecting only the children to be rendered. #prefix and
+    // #suffix should not be inherited for the children.
+    $build = [
+      '#theme' => 'common_test_foo',
+      '#children' => '',
+      '#prefix' => 'kangaroo',
+      '#suffix' => 'unicorn',
+      '#render_children' => TRUE,
+      'child' => [
+        '#markup' => 'kitten',
+      ],
+    ];
+    $setup_code = function() {
+      $this->themeManager->expects($this->never())
+        ->method('render');
+    };
+    $data[] = [$build, 'kitten', $setup_code];
+
     return $data;
   }